Metal envelope tube and method of sealing and exhaust



March 16, 1954 5, 555 2,672,569

METAL ENVELOPE TUBE AND METHOD OF SEALING AND EXHAUST Filed May 20, 1949INVENT Mari L merE. We 5 Patented Mar. 16, 1954 METAL ENVELOPE TUBE ANDMETHOD OF SEALING AND EXHAUST Mortimer E. Weiss, Flushing, N. Y.,assignor to Sylvania Electric Products Inc., a corporation ofMassachusetts Application May 20, 1949, Serial No. 94,380

Claims. 1

The present invention relates generally to the construction ofhermetically sealed and evacuated containers and more particularly toenvelopes for electron devices and the exhaust and sealing of suchenvelopes.

An object of the present invention is the provision 01' a new method forsealing and exhausting a metal envelope electron device and especiallysub-miniature electron discharge tubes.

Another object of the present invention is the provision of an improvedform of metal envelope sub-miniature tube.

Still another object of the present invention is the elimination ofseparate sealing and tipping processes now necessary in the constructionof hermetically sealed envelopes for electrical circuit elements.

A further object of the present invention is to provide a form of tubestructure which will resist the stresses of extreme accelerationsupplied to the tube.

Still a further object of the present invention is the simplification ofelectron discharge tube construction.

The foregoing objects and others which may appear from the followingdetailed description are accomplished, in accordance with one aspect ofthe present invention, by providing an envelope which may be evacuatedand sealed and which comprises two main parts. header, comprises a metaleyelet having a flange at one end and a button of glass sealed in thetubular part of the eyelet. The lead-in wires for connection to theelements within the tube pass through and are sealed into the glassbutton and the operative structure within the tube is supportedprimarily by extensions of the lead-in wires within the interior of thetube. The second main part of the tube envelope is a tubular metal canclosed at one end and having a flange at the other. The metal closure orcan may be an active element of the tube such as the anode in a pentodestructure or it may, if desired constitute at least in part, a supportfor a closespaced anode of a triode structure. The envelope is assembledby replacing the flanged metal can over the header eyelet with theflanges in contact. They are then spot welded together to hold themtogether as a single unit. The unit is then inserted in a small bell jarconnected to an exhaust port of an exhaust machine which may be ofconventional form. The bell jar and the tube unit within are thenexhausted according to a schedule applicable to such machines. The tubeenvelope may be heated by induction in several stages of the exhaustschedule. In the final exhaust, a. heating coil may be placed over thebell jar whereby a very concentrated radio frequency field is coupled tothe adjacent flanges of the envelope causing them to flash weld.Thereafter the evacuated tube may be removed from the bell jar and aconductive get- One part, the 5 ter ribbon between one of the externalleads and the enclosing envelope flashed electrically to complete theactivation of the tube.

The present invention will be more fully understood by reference to thefollowing detailed description, which is accompanied by a drawing. inwhich Figure 1 illustrates in exploded eleva-- tional view an embodimentof the present in-- vention, while Figure 2 illustrates in partialsection a bell jar exhaust arrangement for use with the tube structureof Figure 1.

The exploded elevational view shown in Figure 1 includes a metal can l0hermetically closed at one end by a header l2 and having an outwardlyextending flange M at the other end. The envelope is completed by a baseheader l5 including a metallic eyelet having a tubular portion it and anoutwardly extending flange l8. Sealed within the tubular portion Hi ofthe eyelet is a glass button through which lead-in conductors 24 pass.To the upper end of lead-in conductors 24 are attached the severalinternal elements of the tube. In the specific example illustrated inFigure 1, there is included a filamentary cathode 26 attached at itslower end to one of the lead-in conductors 24 and at its upper end to atensioning arrangement 28. The tensioning arrangement 28 is supported ona rod 3i! passing through spacers 32 and 39. At its lower end, rod isconnected to another one of the lead-in conductors 24. A number of grids36 and 38 are concentrically arranged about the cathode 2t and aremaintained in position by side rods 40 passing through spacers 32and-39. Appropriate ones of the side rods 40 are also connected tolead-in conductors 24. In the pres- ;ent embodiment the anode of thetube is conthe metal envelope is entirely shielded from the influence ofexterior fields, it is contemplated that the evacuated envelope begettered by the use of a conductive ribbon getter 46 connected betweenflange I8 and one of the lead-in conductors 24.

The electron discharge device according to the present invention ispreferably assembled by telescoping the two sections shown in Figure 1together and spot-welding flanges l4 and [8 to- I gether in one or morepoints in order to main tain their relative position. The unit as thusassembled is inserted as shown in Figure 2 on an exhaust port 50 of anexhaust machine. Port 50 is a conductive tube which may if desired beslit for a distance along its length as indicated at 5| in order toinsure that it is not excessively heated by the radio frequency fieldused for bombarding and sealing the tube. The port 50 is conductivelyconnected to the frame structure of the exhaust machine. One of leads 24which is connected to filament 26 is bent outwardly toward one side farenough so that it contacts the exhaust port 50. The others are groupedtogether so that they contact a central inner tube 52 which is insulatedfrom the remainder of the structure by heavy rubber tubing 53. By makinga connection of a source of power to the frame of the exhaust machineand to the inner tube 52, lighting power for the filament 26 as may berequired during the exhaust stages is provided. The discharge tube as awhole is covered with a glass bell jar 55 which fits within acompressible rubber sealing sleeve 55. Sleeve 55 is compressed about thelower end of bell jar 55 by a compression ring 51 threaded over a mountmember 58. Vacuum is applied to the tube through, exhaust tube 52 asindicated, by the arrow at the lower end of Figure 2. As the ex.- haustproceeds, the tube unit may be heated by an external bombarding coilsuch as coil 60 as required. In the final exhaust stage, a veryconcentrated radio frequency field of, say 580 kilocycles, is applied bymeans of another coil 50 closely coupled to the flanges i4 and it. Thismakes a radio-frequency flash weld in a small number of cycles ofalternation of the 60 cycle supply voltage for the radio frequencygenerator, say from 2 to 5 cycles. Thus the interior of. the tubeenvelope is hermetically sealed in from i,- to $3 of a second.Thereafter, the compression ring 51 is loosened, relieving, the pressureof the rubber sleeve 58 against the lower end, of hell jar 50. Bell jar55 is removed and the completely exhausted electron discharge tube isremoved from the exhaust machine. A suitable source of potential isapplied. between the. metal envelope Ii andthev one of lead-inconductors 24 which is connected to the internal ribbon getter 46 thusflashing. the getter.

It will. thus be seen that I have provided an improved type of metalenvelope tube. which. may be: made of any convenient size: including theextremely small sub-miniature sizes and which doesv not require separatesealing and tipping processes normally necessary with. glass envelopes.The. construction has been simplified since the metal envelope mayconstitute an active element oi the tube or itmay be used in aconventional manner to. support a close-spaced. anode for a triodestructure. The elimination of a separate. anode structure and thesleeves neces Sm to anchor the supporting micas tothe anode leads:facilitates assembly. It should be noted that the flanges provided onthe. stem portinn and. on the canportion serve a double purpose. Theyprovide the necessary stress relief for the glassbase-header from thethermal shock which would occur in welding if the flange were notprovided. Because of the comparatively large diameter of flanges I1 andI8, the radio frequency flux used in welding is confined to the outerperiphery so that the weld which occurs is restricted to a very narrowzone around the extreme outer edge of flanges I4 and 18. While I haveparticularly shown and, described an embodiment of the presentinvention, it should be distinctly understood that my invention is notlimited, thereto, but that modifications withinthe scope. of. theinvention. may be. made.

What I claim is:

1. An electron device containing circuit elements within a sealedcasing, said casing including a flanged metal body part and a headerpart, said header part including a flanged tubular metal eyelet having abutton of insulating material within the tubular part and a number oflead-in conductors passing through said button, said flanges beingwelded together around their outer peripheral edges.

2. An electron device containing circuit elements within a sealedcasing, said casing including a flanged metal body part and a headerpart, said header part including a flanged tubular metal eyelet having aglass header button within the tubular part and with a plurality ofleadin conductors passing through said button, said flanges beinghermetically joined together in a.

narrow zone about their outer peripheral edges. 3. An electron dischargedevice including a.

casing having two parts, one being a flanged metal can and the other aheader part including a flanged tubular eyelet having a glass headerbutton within the tubular part, lead-in conductors passing through saidbutton at least a cathode and a number of control electrodes surroundingsaid cathode mounted within said casing and connected to saidconductors, a number of insulating washers secured to said controlelectrodes and having their edges bearing against the interior of saidcan and said flanges being hermetically sealed together around theirperiphery, said can serving as an anode for said device. 7,

4. The method of fabricating, a sealed electron device which incompleted form includes a flanged hollow metal body part and a headerpart including a flanged tubular eyelet and lead-in conductors passingthrough insulating material 5.. The method of fabricating a sealedelectron.- device which in completed: form includes a flanged metal bodypart and a. header part including a flanged tubular eyelet and lead-inconductors passing throughinsulating material.

inthe tubular portion of said eyelet which, in-

cludes the steps of placing said twoparts together with the: flangescontacting one another, placing said devicein an evacuated container toevacuate the space within said device, heating the outer periphery ofsaid flanges with a high frequency field to cause a complete peripheralweld. and thereafter. removing; said device from within.

said container;

MORTIMER E. WEISS...

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date Re. 21,163 Rose, Jr. July 25, 1939' 2,162,234. Thomas l June13, 1939 2,181,366 Edwards etral'. Nov- 28, 1939*. 23855939 Green Dec.26, 1939 2229;436 Beggs 1 Jan. 21, 1941" 2,425,593 Brim Aug. 12', 1 94?

